The present invention relates to a device for determining a 3D structure of an object, comprising a first laser emitter, which generates laser radiation with a first wavelength, and a second laser emitter, which generates laser radiation with a second wavelength. The two wavelengths differ from one another. The device furthermore comprises a first beam splitter, which divides the laser radiation of the laser emitters into a reference radiation and an illuminating radiation, the illuminating radiation impinging on the object to be measured, being reflected by the object as object radiation and interfering with a reference radiation. A detector detects the interference patterns resulting therefrom.
Such devices are used, for example, in dental technology for scanning individual teeth or whole dentures. For example, if a denture model of a patient is to be created, the scanning of the real denture can be performed completely without contact. The production of impressions directly on the patient is thus eliminated completely.
Such a device is known from EP 13 165 409. It works according to the principle of digital holography. At least two laser emitters emit laser radiation of different wavelengths. This is divided into a reference radiation and an illuminating radiation by means of a beam splitter. While the reference radiation is directed onto a detector via a mirror arrangement, the illuminating radiation impinges on the object to be detected. The illuminating radiation is reflected by the object as object radiation and also directed to the detector. Reference radiation and object radiation of one wavelength interfere with one another. The resulting interference patterns are recorded by the detector. If, for example, a tooth is to be measured three-dimensionally, speckle scattering light, which falls at least partially on the detector, is produced by the illuminating radiation and impinges on the rough surface of the tooth. Depending on the surface roughness and the scattering behavior below the surface, a portion of scattering light is also produced, which falsifies the measuring results as speckle noise.